revlog: use `iter(callable, sentinel)` instead of while True
This is functionally equivalent, but is a little more concise.
-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-256-CBC,ADE9D82AA8D8023CD4E9B67FECD9FE08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-----END RSA PRIVATE KEY-----